Focused exploding bridge wire assembly for electric igniters



Aug. 9, 1966 R -rs ETAL 3,264,991

FOCUSEEEXPLODING BRIDGE WIRE ASSEMBLY FOR ELECTRIC IGNITERS Filed April 15, 1965 Robert E. Behs Ncnhcm P. Williams Jr.,

INVENTORS. M771, 1 BY M J, a, W I? 9. w

ATTORNEYS United States atent 3,264,991 FOCUSED EXPLODING BRIDGE WIRE ASSEMBLY FOR ELECTRIC IGNITERS Robert E. Betts and Nathan P. Williams, Jr., Huntsville,

Ala, assignors to the United States of America as represented by the Secretary of the Army Filed Apr. 13, 1965, Ser. No. 447,926 8 Claims. (Cl. 102-'28) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates to an improvement in exploding bridge wire type electric igniters, squibs, detonators, and the like devices. More particularly, the present invention is drawn to a focused exploding bridge wire assembly or arrangement for igniter devices wherein the energy or products of bridge wire explosion are concentrated and directed or focused to a predetermined point, zone or portion of the pyrotechnic of the squib or the like device.

The present invention contemplates using a reflector element having a reflective surface contiguous a portion or portions of the exploding bridge wire for directing the explosion to a desired predetermined area of the pyrotechnic.

A focused exploding bridge wire arrangement according to this invention may be used advantageously, for example, in the missile field for initiating the burning of solid propellants in rocket engine ignition and for activating pressure vessels, switches and the like devices.

In commonly used igniters of the exploding bridge wire type, for example, as disclosed in a prior Patent No. 3,100,447 by Robert E. Betts, the design criteria is greatly controlled by matching the exploding bridge wire with the pyrotechnic and by varying the volume of the pressure chamber, i.e., the space surrounding the bridge wire, between the end plug and the pyrotechnic. In addition, devices in general use require some means for directing the high pressure, high temperature explosion from the pressure chamber to the pyrotechnic.

Accordingly, in view of the above, it is an object of the present invention to provide an improved bridge wire focusing assembly for squibs and the like devices with feature wherein the explosion of the wire is directed in a concentrated manner by a reflector to a particular point or zone of the pyrotechnic.

Another object of the present invention is to provide an exploding bridge wire arrangement which is effective as the sole means for directing the explosion, thereby eliminating the need for a pressure chamber for confining the explosion.

A further object of this invention is to provide an exploding bridge wire arrangement capable of use in firing secondary explosives through a barrier.

A still further object of the invention is to provide an exploding bridge wire arrangement which is particularly useful as a research tool.

The foregoing and other objects of this invention will become more fully apparent from the following detailed description and from the accompanying drawing, wherein:

FIGURE 1 is an elevational, sectional view of a typical electric igniter utilizing an exploding bridge wire arrangement in accordance with the invention;

FIGURE 2 is an enlarged cross-sectional view taken along line 22 in FIGURE 1;

FIGURE 3 is an enlarged view, in cross-section, of another embodiment of the invention; and

FIGURE 4 is an enlarged view, in cross-section, of still another embodiment of the invention.

Referring to the drawing (FIGURE 1) wherein, for

the purpose of illustration, there is shown a typical igniter or squib 1 having the elements thereof housed in a casing 2, which may be formed of a metal such as aluminum. A suitable pyrotechnic or the like explosive charge 3 is molded or otherwise retained as by plate 4 in the closed end of the casing. An end plug 6, of phenolic or the like insulating material, is disposed within the opposite, open end of the casing for enclosing the same. A pair of insulated lead wires 8 extend through the end plug and interconnect the opposite ends of an exploding bridge wire 10. To provide means for effecting explosion of the bridge wire, a source of electrical power (not shown) is connected with the lead wires externally of the casing. To focus or concentrate the energy or products of bridge wire explosion to a desired area of the pyrotechnic, a suitable reflector element 12 is securely positioned between the inner face of the end plug and the bridge wire. In the preferred arrangement, the bridge wire is disposed coextensively within the reflector element, i.e., within the walls of the reflector element, as depicted in the drawing.

In operation of an igniter device such as that shown (FIGURE 1) and utilizing a focusing bridge device such as that shown, for example, in enlarged form (FIGURE 2), a source of electrical power (not shown) is connected with the lead wires. When the required electrical pulse reaches the bridge wire, the wire is caused to reach a superheated condition to the extent that the wire explodes. According to the concept of the present invention, the reflector element concentrates and focuses the explosive energy, or products of explosion, thus, directing the same to a predetermined point or zone of the pyrotechnic. As illustrated (FIGURE 1), the explosion will be focused and directed through slot or elongated, apertured portion 5 in retainer plate 4 to ignite the pyrotechnic.

Since the explosion of the bridge wire is effectively concentrated and directed to a desired area, the need for a primary explosive, normally of relatively high sensitivity, is obviated when igniting a secondary explosive, normally of relatively low sensitivity. Moreover, for the same reason, an explosive may be initiated through a barrier or barriers. Hence, in the use of an arrangement as disclosed herein, not only is the electrical safety of electro-explosives improved, but the hazards normally associated with the handling of highly sensitive primary explosives are eliminated. It is, thus, seen that a highly reliable exploding bridge arrangement having true detonation is provided by the invention. The improved bridge arrangement is usable with any arrangement wherein an explosive is to be ignited, the igniter arrangement illustrated (FIGURE 1) being merely a single, particular application.

A further embodiment of the improved bridge wire assembly is depicted in FIGURE 3, wherein a parabolically shaped reflector element 12 is utilized for focusing the explosion of the bridge wire to a predetermined area of the pyrotechnic. This reflector element has a parabolic reflecting surface which functions in similar fashion to the V-shaped reflector of FIGURE 2 in that the concentration of energy from the explosion in a confined volume, i.e., within the confines of the reflector walls, creates a very high temperature and pressure condition for direction thereof to a specific area of the pyrotechnic to ignite the same.

FIGURE 4 illustrates another embodiment wherein an exploding bridge wire 10 having non-wire particles 11 embedded therein is utilized with a reflector. The embedded elements may include gases, solids, or liquid particles. Thus, upon explosion of the bridge wire, these particles will be directed to the pyrotechnic at high velocities by the reflector surface.

It is apparent that numerous, different reflector elements may be employed. For example, these elements may vary as to the type reflective surface, size, shape and relative location with respect to wire and pyrotechnic, each depending on the desired results.

From the foregoing description it will be readily apparent that a new and improved exploding bridge wire arrangement is provided wherein the explosion of the exploding bridge wire is concentrated and focused to a predetermined point or portion of the pyrotechnic or the like charge disposed in contiguous relationship therewith.

It is to be understood that the forms of the invention shown and described herein are preferred embodiments, and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of the invention, or the scope of the subjoined claims.

We claim:

1. A focused exploding bridge wire assembly comprismg:

a non-metallic plug having a planar end face;

a pair of insulated lead wires extending through said plug in a direction normal to said face;

an exploding bridge Wire extending in contiguous relationship with said face and in a plane parallel thereto, said bridge wire being interconnected at the opposite ends thereof with said lead wires; and

a reflector device positioned between said bridge wire and said end face for focusing the explosion of said bridge wire to a predetermined arera remote from said end face.

2. A focused exploding bridge wi-re assembly .as set forth in claim ,1, wherein the reflector device is V-shlaped and is oriented with relation to the bridge wire so as to focus the explosion outwardly of the open portion of the V-shaped structure.

3. A focused exploding bridge wire assembly as set forth in claim 1, wherein the reflector device is provided with a parabolic reflecting surface.

4. A focused exploding bridge wire assembly as set forth in claim 1, wherein the exploding bridge wire has non-wire particles embedded therein, whereby, upon explosion of said bridge wire, said particles are directed at a predetermined velocity to a predetermined area remote from the reflector.

5. A focused exploding bridge wire assembly for use with an electrically fired igniter, the combination comprising:

a casing having a closed end and an opposite, open end;

a pyrotechnic charge disposed within said closed end;

an end plug enclosing the open end of said casing so that one of its faces is juxtaposed said pyrotechnic;

a pair of insulated lead wires extending through and beyond said end plug;

a focused exploding bridge wire positioned in spaced relationship with said end plug and extending in a plane parallel to said face that is juxtaposed said pyrotechnic, said bridge wire being electrically interconnected at its opposite ends with said lead wires; and

a reflector element secured between an intermediate portion of said bridge Wire and said face, whereby upon energization of said bridge Wire causing the same to explode the explosion will be concentrated and directed by said reflector element to a predetermined area of said pyrotechnic charge.

6. A focused exploding bridge wire assembly as defined by claim 5 wherein a retainer plate is provided within said casing for retaining said pyrotechnic charge therein, said retainer plate having a centrally disposed aperture formed therein, whereby said explosion will be directed through said aperture to said pyrotechnic charge.

7. A focused exploding bridge wire assembly as defined by claim 5, wherein said reflector element is V- shaped.

8. A focused exploding bridge wire assembly as defined by claim 5, wherein said reflector element is generally parabolic in shape.

References Cited by the Examiner UNITED STATES PATENTS 2,942,546 6/ 1960 Liebhafsky et al 102-28 2,977,878 4/1961 Kinkel et al. 10228 2,988,994 6/1961 Fleischer et al 102-28 X 3,082,691 3/1963 Evans et al. 10228 3,109,372 11/1963 Stresau 102-28 BENJAMIN A. BORCHELT, Primary Examiner.

V. R. PENDEGRASS, Assistant Examiner. 

1. A FOCUSED EXPLODING BRIDGE WIRE ASSEMBLY COMPRISING: A NON-METALLIC PLUG HAVING A PLANAR END FACE; A PAIR OF INSULATED LEAD WIRES EXTENDING THROUGH SAID PLUG IN A DIRECTION NORMAL TO SAID FACE; AN EXPLODING BRIDGE WIRE EXTENDING IN CONTIGUOUS RELATIONSHIP WITH SAID FACE AND IN A PLANE PARALLEL THERETO, SAID BRIDGE WIRE BEING INTERCONNECTED AT THE OPPOSITE ENDS THEREOF WITH SAID LEAD WIRES; AND 